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posted by martyb on Friday December 28 2018, @06:43AM   Printer-friendly
from the ask-Senator-Shelby dept.

Submitted via IRC for takyon

An article at SpaceNews.com asks Is the Gateway the right way to the moon? — the "Gateway" is The Lunar Orbital Platform-Gateway.

This article originally appeared in the Dec. 17, 2018 issue of SpaceNews magazine.

Sometime in 2028, competing for attention alongside a presidential election and the return of the Summer Olympics to Los Angeles, NASA will return humans to the surface of the moon.

A lunar lander will depart the cluster of modules in an elliptical orbit around the moon, called Gateway, and descend. One stage will take the lander to a low lunar orbit and then separate, after which the descent module will handle the rest of the journey to the lunar surface. A crew of up to four will spend days — perhaps up to two weeks — on the surface before boarding the ascent module, which will take them back to the Gateway.

At least that’s NASA’s plan for now. A year after President Donald Trump formally directed NASA to return humans to the moon in Space Policy Directive (SPD) 1, the agency has developed the outlines of a plan to carry that out, while emphasizing the language in the policy to do so in a “sustainable” manner and with international and commercial partners. But as the agency describes two of the biggest elements of the plan, the Gateway and a “human-class” lunar lander, it’s still struggling to sell the proposal to its various stakeholders, including its own advisers.

[The somewhat long article is well worth a read. Notable members of NASA as well as former astronauts weigh in on their views of the pros and cons of such an approach as opposed to direct flights to and from the moon. To my eye, NASA was instructed to make the Deep Space Gateway happen so there was a destination for the Space Launch System (SLS) which currently costs something like $2 billion per year in launch and development costs. By comparison, I recall reading that SpaceX anticipates it can develop its next-generation Big 'Falcon' Rocket (BFR) and Big 'Falcon' spaceship (BFS) — now called "Super Heavy" and "Starship", respectively — for about $2 billion total. --martyb]


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  • (Score: 2) by takyon on Friday December 28 2018, @01:13PM (4 children)

    by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Friday December 28 2018, @01:13PM (#779324) Journal

    LOP-G will never be used as a fuel depot.

    The only thing LOP-G would be good for in my opinion? It could be used to allow humans to assemble and service a giant space telescope. And that could be done more easily at the ISS.

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  • (Score: 2) by HiThere on Friday December 28 2018, @05:29PM (3 children)

    by HiThere (866) Subscriber Badge on Friday December 28 2018, @05:29PM (#779390) Journal

    Sorry, but ISS is the wrong place to build a space telescope. Orbiting the moon has some advantages, particularly if the orbit puts it over the far side of the moon part of the time. That could screen out a lot of the radio noise.

    I really think the far side of the moon is generally a better location, but an orbital position gives you more flexibility over just where you point the thing. Of course, the best position would require a pair of observatories...at opposite ends of Neptune's orbit. But that's not going to happen anytime soon. Still, it would give you a great parallax for most of the sky. (All the sky would require a third observatory well out of the plane of the solar system.)

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    • (Score: 3, Interesting) by takyon on Friday December 28 2018, @07:22PM (2 children)

      by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Friday December 28 2018, @07:22PM (#779433) Journal

      You can send bigger payloads to ISS since it takes less energy to reach that orbit.

      Lunar orbit is not where you want a radio telescope. You want a much larger radio telescope on the lunar surface on the far side. Another acceptable ground telescope would be a zenith telescope [nasa.gov].

      The ISS is a great place to put a telescope. You could have it onboard, nearby, tethered or untethered. Or you could just use the ISS as the construction site. With spacewalks, you can assemble a much larger telescope than would be possible to fit into a rocket's payload fairing, and without the risk of rocket vibrations breaking the telescope. Then you can use the telescope's on-board propellant or ion engines to move it away from the ISS if you wish.

      Ideally, we could assemble modular telescopes in orbit using remote control. But as long as we insist on sending humans to an orbiting space station, we should have them assemble or repair gigantic space telescopes. It's more important than anything else they would be doing there.

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      • (Score: 2) by fyngyrz on Saturday December 29 2018, @01:44AM (1 child)

        by fyngyrz (6567) on Saturday December 29 2018, @01:44AM (#779557) Journal

        The ISS is a great place to put a telescope.

        It really isn't. From time to time, the ISS is forced to maneuver abruptly to avoid orbital space debris. A telescope nearby would have to do the same, which would interfere with long exposures and consume maneuvering fuel at a higher rate than one would really want (because ion thrusters would be too weak to impart the required delta-v, so solar power won't cut it.)

        Another issue is that the ISS's earth orbit is pretty fast, so not a very stable observational point. That means (at a minimum) relatively high-rate gyroscopic correction. An ideal space telescope would be able to remain in a relatively fixed location for long exposures, expending as little energy as possible to track whatever it is looking at.

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        • (Score: 2) by takyon on Saturday December 29 2018, @02:26AM

          by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Saturday December 29 2018, @02:26AM (#779566) Journal

          Like I said, they can move the telescope somewhere else after it is built there.

          But the ability to easily service a telescope (since humans are right there) is incredibly valuable. There has never been an attempt to robotically service a telescope, and there might not be for years to come since it is still considered to be cheaper to just launch a brand new telescope.

          Hubble got a lot of lifespan and improvements out of its servicing missions. Not to mention the crucial early fix of its incorrect optics.

          As for keeping a telescope at ISS, you trade an ideal orbit for lower costs, more payload mass, and easy assembly and ongoing repair and servicing. Humans are committed to the ISS until 2028. If there was a large telescope there, that's 10 years of time in which it could be serviced or even enlarged. You wouldn't need the Space Shuttle or anything special to service the telescope, just the Soyuz, or soon Falcon 9 Crew Dragon 2 or CST-100 Starliner, in order to get astronauts to the station.

          If the orbit isn't ideal, you will still have a sizable fraction of the universe that you can observe. You could also detach a telescope when the ISS is at peak altitude and rejoin it later (both will descend at different rates, and the ISS has flexibility in when it can be reboosted). The ISS orbit has peaked around 435 km. Hubble orbits at around 540 km and its orbit will eventually decay down to where ISS has been, unless it is boosted by something like Dream Chaser [wikipedia.org]. Either way, a space telescope operating at a lower orbit would observe a target in its field of view and potentially spend multiple orbits viewing the target each time. Even if it is not as optimal as a higher orbit would be, the lower costs could be a bigger factor. Send two, three, or twenty space telescopes to the ISS or other space station if you want.

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